The field of this invention is pulsed power technology, and relates to high-voltage, high-current components. The disclosed device, in particular, is a high-current, low-inductance, optically-triggered, pseudospark switch.
Many devices, such as particle accelerators, fusion related devices, excimer and free electron lasers, gyrotrons, magnetrons, and electric guns require low inductance, high-repetition rates and high current, i.e., in the range of 10's to 100's of kiloamperes. It is also imperative to have components that exhibit a long operational life if these systems are to transition from the laboratory to viable operating systems.
These high-power systems generally require a switch such as a thyratron, spark gap or pseudospark switch. A pseudospark switch generally exhibits a high repetition rate and relatively low-electrode erosion, and is increasingly becoming a viable switch option when designing high-powered systems.
One such switch, taught by U.S. Pat. No. 4,890,040 issued to Gundersen on Dec. 26, 1989, discloses an optically triggered back-lighted thyratron network containing pseudospark switches which are optically triggered. All known optically triggered pseudospark switches, such as taught by Gunderson, suffer from a problem of metalization of the optical window or optical fiber which occurs as the switch fires. This metalization is exacerbated with use and is a limiting factor in incorporating optical triggering methods in pseudospark switches.
High-power switches can be the limiting component for applications such as charged particle beam accelerators, high-power microwave devices, electromagnetic launchers, and fusion-related devices. Typical performance parameters for this class of switches normally include voltage and current capability, inductance, jitter, delay, current rate-of-rise, energy dissipation, current reversal tolerance, and lifetime. The achievement of acceptable performance by a single switch design based on any particular element alone is not exceedingly difficult, but taken together, the task is quite challenging. The PseudoSpark discharge Switch (PSS), and its optically triggered counterpart, the Back-of-the-cathode Light activated Thyratron (BLT), is one particular switch designs which hold promise of achieving simultaneous improvement in the aforementioned parameters.
The BLT switch as taught by Gunderson above, has an advantage over the pseudospark switch in that it provides for optical isolation of the trigger circuitry, a major advantage in pulsed-power applications. The problem, however, is that the light necessary to initiate the discharge must pass through a window or optical fiber. This window or fiber can become metalized over time by material evaporated from the switch electrodes during current conduction. This results in a reduced switch lifetime, a major concern in repetitive pulsed-power systems.
Another disadvantage with existing high-current BLT switches is that the current is limited to a single channel resulting in electrode erosion, relatively high inductance, and a short operational life. Recent developments in pseudospark discharge switches indicate that multichannel operation holds promise of higher current capability with reduced electrode erosion and lower inductance. A discussion of multichannelling in a pseudospark switch is contained in the proceedings of the VIII IEEE Pulsed Power Conference on pages 472 through 477 in an article entitled Pseudospark Switches for High Repetition Rates and High Current Applications authored by K. Frank et al.
The current state of the art in high-power switches fails to provide an optically triggered, multichannel, low-inductance, pseudospark switch that can provide a satisfactory operational life.